<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body></body>
</html>
<script>
  let xhr = new XMLHttpRequest();
  xhr.open("get", "http://chst.vip/weather/getWeather?key=all");
  xhr.send();
  //   onload的时候ready已经是4了
  // onload比onreadystatechange慢一点
  xhr.onload = function () {
    console.log(xhr.responseText);
  };
</script>
